Algodoo

Short awnser: Surface tention.
Long awnser: The water molecule consists of two Hydrogen atoms and one Oxygen atom. Oxygen has a higher electronegativity than Hydrogen, so it attracts more electrons. This makes the Hydrogen atoms more positive and the Oxygen atom more negative. This dipole causes the molecules to attract each other, and attraction wants the smallest ammount of outsides and just enough insides, what is the best shape for that? Sheres. However, droplets are not perfect solid spheres, gravity wants to push the droplet down, squeezing it. making some sort of elipsoid. TL;DR: Water is a polar molecule and that allows it to attract water and at the smae time, shaping it into a spherical shape, gravity pushes the "sphere" down, squeezing it into an elipsoid. Hopefully you now know why drops of water are round blobs. Fun fact: Water's full chemical name is Dihydrogen monoxide.